John Nisbet had the house built in 1753 on the south side of the harbour, allowing him to develop his business of smuggling goods in and out of the port.
A presentation to mark the occasion was made on Saturday at Netherbyres House, where Clan chief Doctor Mark Nesbitt gave Colonel Simon Furness an antique tea poi to add to the collection of furniture gathered in the house ready for its reopening as a visitor centre.
President David Nisbet, who is stepping down from his role after nearly 25 years, explained the significance of the tea poi to the Nisbet dynasty and Gunsgreen House.
"A tea poi is used to make tea and in 1784 Prime Minister William Pitt abolished tea tax. Three years later, merchant John Nisbet was out of business as there was no longer any need for tea to be smuggled into the country."
Saturday's 25th celebrations were witnessed by 20 members of the Nesbitt/Nisbet clan, with two - Maria Ruchart (nee Nisbet) and Doctor Frederica Hoech - coming from the Munich branch in Germany.
The group received a tour of Gunsgreen House by Col Furness and administrative manager Derek Janes. They then moved to Netherbyres House, where the presentation was made to Gunsgreen House and Col Furness gave a detailed talk on the past, present and future of Gunsgreen House.
He told Nesbitt/Nisbet members that the coach house attached to Gunsgreen had been renamed Nisbet's Tower in memory of their smuggling relative and would be used as a self catering apartment for holidaymakers.
The society's general meeting was also held, where Peter Nisbet stood down after 25 years service as secretary and treasurer, before next year's International Homecoming Gathering and Games, to be held in Edinburgh, was discussed.
A traditional Scottish high tea was then enjoyed at Eyemouth Golf Club.
David Nisbet added: "The society was started to provide genalogy information and a friendship to all clan members worldwide. We now have active members from USA and Australia.
"Saturday provided an excellent day for all."
The 2007 gathering was held in Livonia, Michigan. It has previously been staged at Duns in 2004, where 30 members from North America visited Nisbet House at West Nisbet.
The pele tower was first contructed in the 12th century and was incorporated into the east end of the fortified mansion house, built by Sir Alexander Nisbet of that Ilk, in the 1630s. Nisbet House still stands, with an 18th century tower added to its west end.